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Aggressive Sludge Treatment

Aggressive gold sludge: special pump technology delivers long service life without the addition of water

Global demand for gold and silver remains as high as ever. Precious metals are not only sought after by investors, but are indispensable materials in modern industry.

Look behind the scenes

The mixture must first be condensed and concentrated, therefore the water content of the gold slurry should ideally not exceed 40 percent. In the past, centrifugal pumps were typically used in the mining industry for this conveying step, although centrifugal pumps are in fact designed for fluids and therefore require a medium that contains at least 50 percent water. Additional water was hence injected to operate these pumps, accepting the drawback that the added water made subsequent extraction more difficult and costly.

Challenge accepted

In search of alternatives, a pump from another producer was installed in a mining region on a trial basis. However, the pump housing was completely destroyed within just two days. The high abrasiveness of the gold sludge was to blame. The stone particles in the sludge behave like sandpaper, particularly at high speeds, and wear away all surfaces extremely quickly – until the system fails completely.

Excellently solved

This effect can only be reduced by particularly smooth pumping at an economically viable volume, as further tests with a NEMO® progressing cavity pump demonstrated. To achieve a system with as long a service life as possible, despite heavy wear, the designers at NETZSCH selected tungsten carbide for the rotor. Tungsten carbide, with a scratch hardness of 9.5 on the Mohs scale, is almost as hard as diamond and is therefore scarcely affected by the grinding of the crushed stone. SBE, a nitrile material, was used for the stator. It is similarly extremely wear resistant, but also soft enough to prevent the points of contact with the rotor from wearing out too quickly. The progressing cavity pumps are also low power consumers and are easy to clean and maintain, which in turn reduces operating and maintenance costs. However, it is the durability of the pumps which is decisive when it comes to conveying gold. In the first test, the pump ran for three months without damage to the stator or rotor. The mine operator has since installed further three NEMO® pumps with an average service life of approximately 3.5 months. The service life exceeds the life cycle of earlier centrifugal pumps, which were completely worn out after three months, despite the addition of water.

Products

The NEMO® SY Progressing Cavity Pump is used for demanding applications in every branch of industry around the globe. In bearing block design with free shaft extension, this pump can be run with any type of drive, such as servo motors, diesel motors or hydraulic drives.

NEMO® Pump BY

NEMO® BY Progressing Cavity Pumps can be used in any area of industry where a great variety of different substances must be pumped or very precisely dosed.

NEMO® C.Pro®

The NEMO® N-Ipos CY C.Pro® Dosing Pump is a fully synthetic pump for the precise dosing of a great variety of chemicals in environmental technology and the chemical industry. Its synthetic construction makes it perfectly suited for the gentle and low-pulsation conveyance and dosing of aggressive or non-aggressive chemicals.

TORNADO® Industrial Rotary Lobe Pumps T2

The TORNADO® rotary lobe pump is a positive displacement pump. The pumping action is generated by the contra-rotation of two rotors within the pump chamber which are synchronised externally. The media enters the pump chamber through the inlet port and is carried around the chamber by the rotors to the outlet port where it is discharged.

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